Ninety minutes after feeding mice a single modest dose of the compound epicatechin, found naturally in dark chocolate, the scientists induced ischemic stroke by essentially cutting off blood supply to the animals’ brains.

They found that the animals that had preventively ingested the epicatechin suffered significantly less brain damage than the ones that had not been given the compound.

The study appears online in the Journal of Cerebral Blood Flow and Metabolism.

And while most treatments for stroke in humans have to be given within a two- to three-hour time window to be effective, epicatechin also appeared to limit further neuronal damage when given to mice as much as 3.5 hours after a stroke.

Sylvain Doré, associate professor of anesthesiology and critical care medicine and pharmacology and molecular sciences at the Johns Hopkins University School of Medicine, says the study suggests that epicatechin can stimulate two previously well-known pathways that shield nerve cells in the brain from damage.

The amount of dark chocolate people would need to consume to benefit from its protective effects remains unclear, Doré notes, since he has not studied it in humans. But Doré says his team’s research suggests the amount needed could be quite small. The reason: The suspected beneficial mechanism is indirect and the epicatechin is needed to jump-start protective pathways already present within the cells.

“Epicatechin itself may not be shielding brain cells from free radical damage directly, but instead, epicatechin and its metabolites may be prompting the cells to defend themselves,” he says. “Even a small amount may be sufficient.”

Doré eventually hopes his research into the pathways could lead to ways to limit acute stroke damage and possibly protect against chronic neurological degenerative conditions, such as Alzheimer’s disease and other age-related cognitive disorders.

Scientists became intrigued by epicatechin when studying the Kuna Indians, a remote population living on islands off the coast of Panama. The islands’ residents had a low incidence of cardiovascular disease. Scientists who studied them found nothing striking in their genes and realized that when they moved away from Kuna, they were no longer protected from heart problems.

Researchers soon discovered the reason was likely environmental: The residents of Kuna regularly drank a very bitter cocoa drink, with a consistency like molasses, instead of coffee or soda. The drink was high in epicatechin, which is a flavanol, a flavanoid-related compound.

People shouldn’t take the research as a free pass to consume large amounts of chocolate, which is high in calories and fat, Doré notes. In fact, he says, people should eat a healthy diet with a variety of fruits and vegetables.

Not all dark chocolates are created equally, Doré adds. Some have more bioactive epicatechin than others.

“The epicatechin found in dark chocolate is extremely sensitive to changes in heat and light,” he says. “In the process of making chocolate, you have to make sure you don’t destroy it. Only few chocolates have the active ingredient. The fact that it says ‘dark chocolate’ is not sufficient.”

The study was supported by grants from the National Institutes of Health and the American Heart and Stroke Association.